Telephone current-selector.



.that other useful and advantageous results view of one form of mv invention. Fig. 2 is a side elevation of li`i 1 Fig. 3 is a plan view-of a modified ma of m invention. Fig. 4 is a side elevation o Fig. 3.

985,024. TELEPHONE CURRENT-SE- LECTOR. EUonNs Ganas'rson, Buffalo, N. Y., assignor of five one-hundredths to i Christopher H. `Bierbaum, ten one-hundredtlis to Arthur L. Fox, and thirt -five onehnndredths to Geer e H. Ca kins,l Buffalo, N. Y., twelve an one-half onei hundredths to George R. Fuller and twelve and one-half one-hundredths to J. W. Morrison, Jr., Rochester, N. Y. and twenty one-hundredths to Harold F. Hayes. Filed May t3, 1908. Serial No. i 430,971.

To all whom it may concern:

lie it known that I, EuosNnGAiinsrsoN, a citizen of the United States, and a resident of the cit of ltufialo, county of Erie, and State of i ew York, have invented certain new and useful improvements in Teleihoiie Current-Selectors, of which the following is a full, clear, and exact description.

My invention relates to telephone current lselectors generally and has for its chief ob- 1iectthe production of means for distinguishing between various pressures on telephone circuits, as applied to telephone ringers or i other mechanism.

lt will be clear to those skilled in the art will follow from the use of my invention as herein described.

l't is well-known that condensers have been used for the purpose of obtaining the object above set forth but such condensers have been, when practically applied both cumbersome andl expensivess well as fragile and linbleto puncture by static discharges.

By means of the invention herein de= scribed the object. above set forth is attained in such a way that the device is much cheaper, less cumbersome and more reliable than the condensers heretofore used for such purposes and moreover it is much sim ler in construction and more easily insta led l than a condenser.

Referring now drawings in which like characters of refereiiee indicate corresponding parts tliroii hout the different figures, Figure 1 is a p an Fig. 5 shows my invention as applied to a telephone circuit.

1 is a base of' any suitable insulating mnterial u on which are mounted conducting terminas 2.

3 is a filament of argentite or other metal-l lic oxid or com ound. This filament ia` suitably connecte to the terminals 2.

Referring now to the modified form of my invention as shown inFigs. 3 and 4, the sanie insulating base 1 is used in this form to the accompanying..

. and the resistance o 'as in tli--f'urlioivAh-Tii-Fi biiiidh-a nd .l likewise I- iise in this form a filament 3 ofi the same character as the filament B shownf in Figs. 1 and 2. The filament in Figs. iigand 4 is in contact with the clip terminals 4. -These cli terminals 4 are of such nia' terial and ariiustment that a contact rcsistl ance exists between them and the filamenti 3. As is well-known a contact resistance varies .with and is greatly dependent upon the ressure of the current flowing so that by tiis means I am able to attain a rreater selective efl'ect between currents of different pressures than it is possible to attain by v means of the conducting terminals 2.

Either the form of mv invention shown in Figs. 1 and 2 or that shown in Figs. 3 and 4 may be applied to a telephonie circuit in the manner s iown in Fig. 5. l ln this figure the wire 5 is a part of a circuit from a constant or regulable source of energy and wire (i is inthe saine circuit. 7 represents a ringing mechanism or any other electrically operated telephone device of the usual construction used in telephonie circuits. The device 7 is connected with the wire 5 'by wire 8 and is connected to one of the terminals of my selective device hy the wire fl; the other terminal of my selective device being in turn connneeted to the wire hy the wire 10.

I have already described the characteristics of the filament 3 but it should be here noted that in the preparation of this filamentl prefer to use those compounds which have a ne tive. temperature coefficient. With such a' filament the heat generated by the leakage current at moderately. low' pressures being neglipibly small is radiated the filament remains A sufficiently greater constant. pressure however causes a current to flow w iich effects a rise of temperature in the. filament and reduces its resistance whcrcb the selective eflect obtained is much en ianccd.

Itfwill be clear to those skilled in the art that b use of my invention as above de e scribe( I ani able to maintain in telephonie circuits a fixed and hi h resistance at low prcsfures thus preventing the flow to any grea extent. of currents, but which at higher pressure permits the tlowof currents greater in proportion thereto (or disproportionally large to such increased pressure). In a particular adaptation of my invention as shown in Fig. 5 a battery pressure of some certain voltage will cause ittle leakage through a high resistance filament such as 3 but a greater current o f increased pressure eniployed for actuating themechanism will cause a renter flow of current which is am ly sullicient for the purpose.

Il., will be understood of course, that thc resistance of the filament 3 may be regulated in proportion to the pressure of the current used. Such filament resista-ncel being suchi that. but a slight current ivill flow at moderately low pressures but at hi her pressuresl a suiliciently great current'wili How Ifor the purpose desired.

It will be understood of course that it iscl not necessary to use in my invention a re-' sistauceY material in the form of a filament but 'instead thereof we may ilse a bar or other conductor of suitable form having the characteristics of the filament as hereiny before described. It will be further evident l to those skilled in the art that the characters of the contact resistance as shown in Figs. 3 and 4 may be varied somewhat as desired by composition, form and mechanical adjustments of the various parts.

Having thus described my invention, what l claim is:

1. In a tele. )hone circuit the combination with a regulaiile source of energy, an electrically actuated device and a circuit con necting said device with said source of energy; of a variable resistance unit cornprising a filament of resistance material having a negative temperature coefficient and being connected between the terminals of said source of energy whereby when the said material conducts a small fiow of current j the heat generated is radiated butI a fiow of current duo to increased pressure will raise the temperature of the filament and l reduce its resistance, thus enhancing theP current ow and thereby reducing a i great] increased conductive e ect.- i 2. l'ii n tclephonocircuigthe combination with a. regular source of energy, an electrlcally actuated device and a circuit conncct: ing said device with said source of ellpl'gy of a variable resistance unit comprising ai filament. of argentite connected between the? l l terminals of said source of energy whereliv1 when the said argentite conducts a sinn l1 flow of current. the lient. generated is radiated but a flow of current. due to increased iressure. will raise the temperature of the ilament and reduce its resistance thus enhancing the current flow and thereby rodncing a greatly increased conductive e ect. In witness whereof I have hereunto set mv hand in the rcsence of two witnesses. E GENE GARRETSON. lvitnesses:

E'rimr. A. KELLY, G. H. Camcms. 

